US1356226A - Synchronizer - Google Patents

Description

M. L. SEVERY.

SYNCHRONIZER.

APPLICATION FILED MAYI, 1917.

1,356,226, Fatented 00$ 19, 1929.

2 SHEHS SHEET M. L. SEVERY.

SYNCHRONIZER.

my APPLICATION FILED MAYY' 1917. 1,a06,226

Patented Got 19, 1920.

UNITED STATES PATENT OFFICE.

MELVIN L. SEVERY, DE LOS ANGELES, CALIFORNIA.

SYNCHRONIZER.

' Application filed May 7,

To all whom it may concern:

Be it known that I, MELVIN L. SEVERY, a citizen of the United States. residing at Los Angeles, in the county of Los Angeles and State of California, have invented certain new and useful Improvements in Synchronizers, of which the following is a specification.

This invention relates to devicesfor synchronizing the rotary movements of two independently driven and distant shafts.

In my Patent No. 1,186,851 granted June of a sonorous body such as a tuned string.

In various devices too numerous to mention it is necessary to drive independently two separate shafts not only at the same or approximately the same rotative speeds but in a definite and maintained phase relation,

and the present invention involves certain additions to and refinements upon the device of my prior patent to adapt it to use in this last-named field.

I accomplish the result by making use of two of the devices of my prior patent which are initially adjusted to practically equal speeds. One of these is known as the master device and differs from the mechanism .described in my prior patent only in the inclusion of a feature designed to compensate for temperature variations. The second of the two mechanisms. which I call the con trolled device, is the same as the first with the following additions:

1. An electromagnetic means for varying the speed adjustment while the device is in operation;

2. Manually-operable means for effecting an absolute adjustment of the driven element with reference to the driven shaft for the purposeof adjusting the phase of the driven element with reference to that of the driven element of the first device; and

Specification of Letters Patent.

Patented Oct. 19, 1920.

Serial No. 166,969.

tion as outlined above is illustrated in the accompanying drawings, in which Figure 1 is a plan view of the complete mechanism with the electric circuits shown in diagram;

Fig. 2 is a horizontal axial section of the controlled device, certain wiring connections being shown in diagram;

Fig. 3 is an enlarged sectional view showing a centrifugal contact and the electromagnetic means for adjusting same;

Fig. 4 is a-view of the electromagnetic adjusting means of Fig. 3, viewed from the left in that figure;

Fig. 5 is a diagram of the speed-controlling circuit characteristic of the device of my patent above referred to, one such circuit forming a part of the master device and another identical circuit forming a part of the controlled device; and

Fig. 6 is a wiring diagram showing the connections for indicating and maintaining synchronism between the master and the controlled devices. This circuit is wholly independent of the speed-control circuits shown in Fig. 5.

The speed-control mecizam'sm.-As previously stated, this mechanism is substantially that of my prior patent and is described here in order that the additions and improvements hereinafter described may be fully understood. The two mechanisms are substantially identical and all the added features are included in the driven element, so that a description of that element will suffice for both.

Two motors or other prime movers 11 and 12 are used, the motor 11 driving the master device or instrument and the motor 12 the controlled device. The motor 11 drives a metallic annulus 13 preferably of copper, and the motor, 12 drives a' similar copper annulus 14. In each case the driven element whose speed is to be maintained constant consists of an annular shell indicated by the numerals 15 and 16 in Fig. 1. The internal construction of these is the same and'may be determined from an inspection of Fig. 2. In Fig. 2, the shell 16 is provided with an annular series of electromagnets 17, two pairs being shown in this figure. The shell 16 is likewise provided with two slip rings 18 and 19 insulated from said shell and from each other, and bearing on these slip rings are properly insulated brushes and 21. The shell 16 also carries a very light spring switch, the" arm of which is indicated by the numeral 22, this switch contacting withan appropriate contact 23 (see Fig. arm 22 is pivoted at 24 so as to be adjustable by a threaded stem or screw 25, which bears not against the arm 22 but against a member 16 at which the switch 22 will be narily not used on the master brought into touch with the contact 23. The bi-metallic bar 26 is so designed as to compensate .or approximately compensate for the disturbing effects which are otherwise, induced by changes of temperature. Variations in temperature such as may be caused by changes inroom temperature, or by the heating efl'ect duced in the shells 13 or 14, afi'ect in some degree the speed regulative action of the device, and the thermostatic bar 26 is so designed as to compensate or approximately 'ompensate for the disturbing effect mentioned. I

In Figs. 3 and l an electromagnetically operated ratchet device is shown for adjustingthe screw 25. This mechanismin the example shown is used only on the controlled device, and as it forms part of the adjusting circuit will be described hereafter. lit is tobbe understood that this electromagnetic adjusting mechanism is ordidevice, 2'. e. on member 15, but that on this member the screw 25 is manually adjustablefby means of a wheel 27 indicated in'Fig. '1. ll do not,

: however, mean to disclaim its use in cases where 1ts function can be utilized; for example, to make adJuStments when necessary. r Y

The windings of the magnet 17 are connected in series with each other by means of a wire 28, and one endot' this circuit is grounded to the shell,16. The other end is connected to the slip ring 19. Similarly, the spring switch the member 16 and the insulated contact 23 is connected to the slip ring'13. These connections are fully shown in diagram in Fig. 5, and may also be traced out in Figs.

1, and 2 so far as the parts are shown in the respective figures. The brush 20 which runs on the slip ring 13 is connected directly to one end of a resistance 29 whose opposite end is connected through a battery 30 to ground, ground being made by connecting the terminal of the battery to a hearing of the machine as indicated at 31 in both Figs. 1 and 5. runs on the slip ring 19 is connected to one end oi a resistance 32 whose other end is The switch of eddy currents in-' arm 22 is grounded to V the device is in operat on the centrifugal The brush 21 which connected with the circuit between the resistance 29 and the battery .30.

A shunt circuit for cutting out the resistance 32 is made by means of the wires 33 and 34, andis controlled by a switch arm 35 urged open by a spring 36 but at times held closed by an electromagnet 37 which is in cluded in a shunt or bridge connection leading from a point between the brush 20 and resistance 29 to a point between the battery 30 and the ground connection at 31. This circuit is duplicated, one being present in the 29 and. magnet 37 whichcloses the switch 35 and shunts the resistance 32 out of cir.

cuit. When the switch 35 is closed current will freely flow from the battery 30 through the wire 34, switch 35, wire 33, brush 21 and slip ring 19 to and through the windings'of the magnets 17, and, thence through the ground connections back to the battery.

The resistance 32 being shunted out of the circuit, a comparatively heavycurrent will flow and a comparatively heavy torque will be exerted between the copper annulus 13 (referring now to the master device) and the magnets 17 of its corresponding driven member. This will produce an increase in the rotative speed of such driven member, and when this speed is sufficient to'cause the switch arm 22 to close against the contact 23 thecircuit closed through ground will form a shunt around magnet 37 and will so weaken this as to cause switch 25 to open.

as soon as this occurs all the current flowing to the magnets 17 mustflow through the resistance 32. The field of the magnets 17 is thereby correspondingly weakened, and the driving torque between the annulus 13 and the magnet 17 co-acting therewith is reduced.

As pointed out in my prior patent, when switch-arm 22 has a periodic or intermit tent action resulting in a periodic or intermittent action of the magnet relay switch 35, and such action adjusts itself with such nicety as to produce a practically constant speed of the driven elements 15 and 16 regardless of minor speed variations of their respective driving motors 11 and 12, and regardless of changes of load. TV here only one device is involved, the speed regulation is amply close for all ordinary purposes. ii /hen two are involved even a very slight difference in rotative speed would, in the course of time, involve a cumulative error resulting in marked phase difference, objection- I to preserve its phase relation to the master instrument.

Phase-finding mechanism-The member 15, which is the driven member of themaster instrument, is rigidly connected to a wheel or the like, 38, which I have chosen to symbolize the driven member whose speed is maintained constant. What particular mechanism this may be is'immaterial to the present invention. The driven member of the controlled device is represented by a disk or wheel 39. It is necessary not only that the disk 39 turn at the same speed as the disk 38, but also that itbe brought into perfect phase relation with the disk 38 and maintained there. Assuming that the two devices can be started at perfectly equal speeds, and I am able to do this with devices such as shown in the drawings, it is still a fact that they will probably start out of phase. and some means must be provided for bringing them into phase after theyhave started.

Accordingly, in the controlled device the disk 39 is not rigidly attached to the driven member 16 but is swiveled thereto by means of a collar 40. The connection of member 16 and the disk 39 consists of a rod 41 axially slidable in a tube 42, which tube is formed integral with the member 16. The

rod 41 is provided with a longitudinal spline or feather connection 43 with the tube 42,

and is further provided with quick pitch threads 44 which engage the disk 39. Consequently, the angular position of the disk 39 with reference to the member 16 may be adjusted by an axial shifting of the rod 41, and when the rod 41 is positively held in its adjusted position the member 16 and the disk 39 must turn together in the definite angular relation produced by such adjustment. In order to shift the rod 41 to effect the desired adjustment, .1 make use of a rod 45 having a swivel connection to a head 46 on the rod 41, the rod 45 being of square cross section and held against rotation by a square guideway 47. Swiveled on the end of the rod 45 is a threaded sleeve 48 turning in a fixed threaded block 49, and capable of being turned by a crank arm 50. The longitudinal adjustment of the rod 41 is thus effected at a slow progressive rate by turn ing the crank 50, and this adjustment may be made while the machine is rotating.

. In order to indicate when the devices have been brought into phase by such adjustment, I provide the member 15, which as will be remembered is rigidly connected to the disk 38, with a single insulated contact 51 of small extent, and I provide the disk 39 with a similar contact 52. A brush 53 runs on the periphery of the member 15 in co-active relation with the contact 51, and a similar brush 54 runs on the periphery of the disk 39 in co-active relation with the contact 52.

The brushes 53 and 54 are connected together by a wire 55 which may be interrupted by a manually operable switch 55", and certain other connections hereinafter described give an electric impulse when the two brushes 53 and 54 contact with their respective contacts 51 and 52 at the same moment. This impulse is used to indicate that true phase relation has been initiated so that adjustment through the crank 50 will be stopped. It is also used to connect and render operative an automatic adjusting means for the controlled device.

Mechanism for adjusting speed of driven member while running.-The screw 25 of the driven member 16 of the controlled device is provided witha ratchet wheel 55. (See Figs. 2, 3 and 4.) Pivoted' concentrically with the wheel 55 is an arm 56 held in its mid or neutral position by a leaf spring 57. Pivoted on the arm 56 is a double pawl 58 held in its neutral position in which it does not engage the ratchet wheel 55, by a spring 59. The spring 59 is much lighter than the spring 57. .The double pawl carries an armature 60 which swings between the pole pieces of two electromagnets 61 and 62. If either'magnet is momentarily energized it attracts the armature 60, the initial movement overcoming the spring 59 and causing one or the other end of the double pawl 58 to engage the ratchet wheel 55. The further movement of the armature 6O swings the arm 56 against the resistance of the spring 57, and moves the ratchet wheel 55 the space of one tooth. Thus the actuation of the magnet 61 increases the speed at which the centrifugal switch 22 will act to close the circuit, and the actuation of the magnet 62 decreases the speed at which said switch 22 will close the circuit.

()ne terminal of each of'the magnets 61 and 62 is connected by a wire 63 to a brush 64 which contacts with a slip ring 65 on the disk 39. The other terminal of the magnet 61 is connected by a wire 66 to a brush 67 which runs on a slip ring 68 concentric with the slip ring 65. The other terminal nections are traced out in diagram. .The

wires would, of course, be inclosed within the rotary member 16 and sleeve 42. The provision of the brushes 64, 67 and 70 is to permit the relative rotary movement of the member 39 with reference to the member 16.

As already stated the member 39 is provided with an insulated contact 52 described as intended for indicating when the correct phase relation has been attained. The remainder of the periphery of disk 39 is taken up with two other insulated contacts 72 and 73. (See Figs. 1 and 6.) The slip ring 68 is connected to the contact 73, and the slip ring 71 is connected to the contact 72. Consequently, the contact 72 is connected to that magnet which provides a retarding adjustment, and the contact 73 is connected to the magnet which produces an accelerating adjustment of the driven member of the controlled device. The third slip ring 65 is connected to a slipring 74, and through a brush 75 and wire 76 to the right-hand contact 77 of a relay switch hereinafter described. The contact 52 is connected to a slip ring 78, and from that by means of a brush 79 and wire 80 to one terminal of a relay magnet 81. The other terminal of the magnet 81 is connected by a wire 82 to the left-hand contact 83 of the relay switch above mentioned.

This relay switch consists of the contacts 77 and 83, and an arm 84. (See Fig. 6.) The arm 84 is urged to the right by a spring 85, but 'in starting adjustment is latched to the left against contact 83 by means of. a pivoted armature 86 which may be drawn to releasing position by the energization of magnet 81. A spring 87 opposes the action of this magnet. The switch-arm 84 is connected by means of a wire 88 to one terminal of a'battery 89 whose other terminal is connected to a brush 90 running on a slip ring 91 on the driven shaft of the master device, and electrically connected to the contact 51 heretofore mentioned.

Operations-To start the devices into operation the first step is to open switch 55 and latch' the arm 84 of the relay switch to the left by means of the armature 86,

thus closing the contact at 83. The motors 11 and 12 are then started, it being assumed that the centrifugal switches 22 of the two devices are so adjusted that their driven shafts will turn at approximately ]equal speeds. Such adjustment can be made by trial and error, and after the devices have been in operation this adjustment need not be repeated because as soon as the mechanisms are shut down the entire regulating mechanism goes out of action, and leaves the devices in the condition and adjustment at which they had been operating in practical synchronism.

With the two devices in operation at substantially equal speed it is now necessary to bring them into phase. Switch 55 is closed. .Then the crank 50 is turned thus causing the disk 39 to gain or lose with reference to the rotary member 16 of the controlled device. Since the adjustment is relatively slow this adjustment plus whatever slight speed difference there may be between the two devices, will inevitably cause the brush 53 to be against the contact 51 at the mo-' ment that the brush 54 is against the contact 52. At such moment the devices are in the desired phase. The effect of this simultaneous contact of the two brushes 53 and 54 is to cause a current to pass from the battery 89 to the brush 90, slip ring 91, contact 51, brush 53, to the brush 54, and thence through contact 52, slip ring 78, brush 79 and wire 80 to the magnet 81. From the other terminal of said magnet 81 it returns by wayof wire 82, contact 83, switch arm 84, and wire 88 to the battery 89. The resulting attraction of the magnet 81 on the armature 86 unlatches the arm 84 and allows it to move to the right under the influence of the spring 85, so that the arm 84 moves out of touch with contact 83 and into touch with contact 77. This immediately cuts magnet 81 and contact 52 out of circuit, and establishes a circuit from the battery 89 through switch-arm 84, contact 77, wire 76, brush 75, slip ring 74, slip ring 65, brush 64 and wire 63 to one terminal of each of the magnets 61 and 62. The other terminals of these two magnets are respectively connected through the slip ring connections 67, 68, and 70, 71, to the contacts 73 and 72.

If the brush 54 is on the contact 72 at the moment that contact 51 reaches the brush 53, the controlled device has been gaining and must be retarded. This efiect is secured because the contact 72 is connected to the retarding magnet 62, and the impulse sent through the line when the contact 51 reaches the brush 53 actuates the adjusting device to cause thecontrolled device to drive at slightly slower speed. This adjustment will be repeated at each revolution until the brush 54 is on the contact 52 at the moment that contact 51 reaches brush 53. Contact 5 2 is now dead throughthe action of the switch-arm 84.

Shouldthe brush 54 be on the contact 73 at the moment the contact 51 reaches the brush 53, then the controlled device has been losing -with reference to the master device and acorresponding adjustment is made because the contact 73'is connected to the magnet 61 which will receive. an impulse through this contact at the moment that the contact 51 reaches said brush 53. This will adjust the controlled device to turn faster, and thus the controlled device is given a slight tendency to hunt back to its adjustment for synchronism should it depart from this adjustment in 'either direction.

Various other arrangements of the circuit and various modifications of the details of the adjusting mechanism will readily sug gest themselves. The fundamental idea of the invention is the use of two speed-controlling devices, one of which is adjustable while running, together with a phase-finding and retaining mechanism operatively related to the adjusting mechanism of the second or controlled device to adjust it toward its correct phase immediately upon its departure therefrom. Inthe accomplishment of thi desired function the provision of the thermostatic adjustment for the centrifugal switch is of the greatest importance, particularly as the two mechanisms may be widely separated and may be subjected to thermal conditions which are different and which vary at different rates, and hence would otherwise introduce a serious disturbing factor.

It may frequently happen that the two instruments are widely separated, and as a consequence are subjected. to temperature variations which differ widely for the two instruments. The provision of a thermostatic compensating device on eachinstrument to neutralize or approximately neutralize the disturbing effects of temperature, reduces the tendency of each instrument to depart from its constant speed operation, and consequently reduces the necessary corrective action of the phase-maintaining mechanism. A regulation that is sufiiciently close for one instrument is not sufliciently close to maintain accurate phase relation of two instruments. This makes necessary the phase-finding and maintaining mechanism characteristic of the present invention. The thermostatic device by eliminating the disturbing efi'ects of temperature, relieves the phase-maintaining mechanism of considerable work.

Having thus described my invention, what I claim is '1. The combination with two speed controlling mechanisms, each including a driving member, a driven member, a variable ratio drive means interposed between said driving and driven members, and a speed responsive device subject to the speed of the driven member and operative to vary the driving ratio of saiddrive means; of reversible electrically actuated adjusting means for adjusting the action of one of said speed responsive devices while running; a rotary commutating device having two contacts of considerable extent individually connected to said adjusting means to control reverse actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members; and electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device, whereby the second commutating device actuates the adjusting means in a direction controlled by the first commutating device according to the running; a rotary commutating device having two contacts of considerable extent individually connected to said adjusting means to control reverse actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members; and electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device, whereby the second commutating device actuates the adjusting means in a direction controlled by the first commutating device according to the direction of phase displacement of the driven members.

3. The combination with two speed controlling mechanisms, each including a driving member, a driven member, a variable magnetic drag device forming the driving connection between said members, and a centrifugal switch for varying the driving action of said magnetic drag device; of reversible electrically actuated adjusting means for adjusting the action of one of said centrifugal switches while running; a rotary c'ommutating device having two contacts of considerable extent individually connected to said adjusting means to control reverse actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contactof small extent and driven by the other of said driven members; and electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device, whereby the second commutating device actuates the adjusting means in a direction controlled by the first commutating device according to the direction of phase displacement of the driven members.

at. The combination with two speed controlling mechanisms, each including a driving member, a driven member, a variable trifugal switch for varying the driving acmagnetic drag device forming a driving connection between sald members, a cention of said magnetic drag device, and a thermostat operatively related to said centrifugal switch to compensate for local temperature changes; of reversible electrically actuated adjusting means for adjusting the action of one of said-centrifugal switches while running; a rotary commutating device having two contacts of considerable extent individually connected to said adjusting means to control reverse actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members, and electric connections connecting the ad usting 'means and the first commutating device in circuit with the second commutating device, whereby the second commutat ng de vice actuates the adjusting means in a direction controlled by the first commutating device according to the direction of phase displacement of the driven members.

5. The combination with two speed controlling mechanisms, each including a. driving member, a driven member, a variable ratio drive means interposed between said driving and driven members, and a speed responsive device subject to the speed of the driven member and operative to vary the driving ratio of said drive means; of reversible electrically actuated adjusting means for adjusting the action of one of said speed responsive devices while running; a rotary commutating device having two contacts of considerable extent individually connected to said adjusting means to control reverse actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members; electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device, whereby the second commutating device actuates the adjusting means in a direction controlled by the first commutating device according to the direction of phase displacement of the driven members; and manually operable means for effecting a positive adjustment of the angular position of one of said driven members relatively to the other while runmeans; of reversible electrically actuated adjusting means for adjusting the action of 1 access one of said speed responsive devices while running; a rotary commutating device having two contacts of considerable extent individually connected to said adjusting means to control reverse, actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members; electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device, where by the second commutating device actuates the adjusting means in a direction controlled by the first commutating device according to the direction of phase displacement of the driven members; and manually operable means for effecting a positive adjustment of the angular position of one of said driven members relatively to the other while running, to initiate the desired phase relation.

7. The combination with two speed controlling mechanisms, each including a driving member, a driven member, a variableone of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members; electric connections connecting the adjusting means and the first commutating device in circuit with the sec ond commutating device, whereby the second commutating device actuates the adjusting means in a direction controlled by the first commutating device according to the direction of phase displacement of the driven members; and manually operable means for efiecting a positive adjustment of the angular position of one of said driven members relatively to the other while running, to initiate the desired phase relation.

8. The combination with two speed controlling mechanisms, each including a driving member, a driven member, a variable magnetic drag device forming a drivin connection between'said members, a centrif ugal switch for varying the driving action of said magnetic drag device, and a thermostat operatively related to said centrifugal switch to compensate for local temperature changes; of reversible electrically actuated adjusting means for adj ustin the action of one of said centrifugal switches while running; a rotary commutating device having I two contacts of considerable extent individually connectedito said adjusting means to control reverse actuations thereof, and driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of saidvdriven members; electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device, whereby the second commutating device actuates the adjusting means in a direction controlled by the: first commutating device according to the direction of phase displacement of the driven members; and manually operable means for effecting a positive adisolated contacts of considerableextent and justment of the angular position of one of said driven members relatively to theother while running, to initiatethe desired phase relation. I i r 9. The combinationwithtwo speed controlling mechanisms, each including a driving member, a driven member, avariable ratio drive means interposed between said driving and driven members, and a s eed responsive device subject to the speed 0 the driven member and operative. to vary the driving ratio of said drive means; of reversible electrically actuated means for adjusting the action of one of said speed responsive devices while running; a rotary commutating device having two a single inter osed contact, said two contacts being indivi ually connected to said ad usting means to control the reverse actuations thereof, and said commutating, device being driven by one of said driven members; a second rotary commutating device havin a single contact of small extent and driven y the other of said. driven members; electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device; a switch controlling said connections; a magnetic actuator for. said switch controlled by said interposed contact on said first commu ated adjustin means for adjusting the action of one 0 said speed responsive devices while running; a rotary commutating device having two isolated contacts of considerable extent and a single interposed contact, said two contacts being individually conadjusting nected to said adjusting means to control the reverse actuations thereof, and said commutating device being driven by one of said driven members; a second rotary commutating device having a single contact of small extent and driven by the other of said driven members; electric connections connecting the adjusting means and the first commu tating device in circuit with the second commutating device; a switch controlling said connections; a magnetic actuator for said switch controlled by said interposed contact on said first commutating device; and manually operable means for effecting an initial angular adjustment of one of said driven members with reference to the other while the devices are running.

11. The combination with two speed controlling mechanisms, each including a driving member, a driven member, a variable magnetic drag device forming the driving.

connection between said members, and a, centrifugal'switch for varying the drivin ac tion of said magnetic drag device; 0 reversible electrically actuated I adjusting means ffor'ad justing the action of oneof said centrifugal switches while running; a, rotary commutating device having two isolated contacts of considerable extent and a single interposed contact, said two contacts being individually connected to said adjusting means to control the reverse actuations thereof, and said commutating device being driven by one of said driven members; a

second rotary commutating device having a single contact of small extent and driven by the other of said driven members; electric connections connecting the adjusting means and the first commutating device in circuit with the second commutating device; a

7 switch controlling said connections; a magnetic actuator for said switch controlled by said interposed contact on said, first commutating device; and manually operable-means for effecting an initial angular adjustmentof one of said driven members with reference to the other while the devices are run- 7 ning.

12. A speed regulating device comprising in combination a driving member; a driven member; a variable magnetic drag device forming the driving connection between said members; a centrifugal switch for varying the action of said magnetic drag device; and a thermostat operative upon said centrifugal "switch to compensate for the effect of temperature variations.

1?). A speed regulating device comprising in combination a driving member; a driven member; a variable ratio drive means interosed between said driving and driven memers; a 'centrifugally actuated device for varying the driving ratio of said drive means; and a thermostat o erative upon said centrifugally actuated evice to cominsenee ling said di'ive means; and a thermostat operative upon said switch to compensate for the efl'eets of temperature variations. 10

In testimony whereof I have signed my name to this specification.

MELVIN L. sEvEnY.

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